1. Field of the Invention
The present invention relates to a device for crushing rocks by the utilization of fluid pressure and more particularly, to a device for crushing a rock or concrete by the insertion thereof into a borehole formed in the rock or the concrete to be crushed.
2. Description of the Prior Art
Generally, a blasting method has been most commonly used for crushing rocks or concrete which, however, is disadvantageous in that noise and dust are inevitably generated upon blasting to affect not only the environmental conditions but also the operation conditions in the pit, inducing critical influences on safety in operation. Therefore, a rock crushing method has been strongly desired that can reduce the amount of noise, vibrations and/or dust generated at crushing, when compared with the prior art crushing method.
From the above viewpoint accordingly, there has been a method in recent years that rocks to be crushed (hereinafter referred to as an object to be crushed) are preliminarily formed with boreholes before being crushed, and then, a fluid material is pumped into the boreholes. This method which utilizes the pressure of the fluid material is called a collapse method. According to this collapse method, however, if there is observed any crack or any crevice in the object to be crushed, a serious problem occurs in that necessary pressure for crushing the object to be crushed cannot be obtained because of the leakage of the pressure fluid out of the crack portion.
In another method, a limy filling is used for crushing. The limy filling which has been preliminarily plugged into the boreholes formed in the object to be crushed is expanded through chemical action, and thereby the object statically crushed. According to this method, however, it takes a relatively long time for the limy filling to be expanded through chemical action, and therefore, it is disadvantageous due to low operational efficiency and high operational cost.
Furthermore, in the prior art crushing methods as described above, the crushing force against the wall of the boreholes acts approximately uniformly on the object to be crushed in the circumference of the boreholes, and many cracks are generated on the object to be crushed. As a result, in the case of a tunnel excavation employing the prior art crushing method, for example, the wall surface of the tunnel of a desired shape is formed with many cracks to be a coarse and rough surface, with the ground around the tunnel being loosened, and therefore, it is inconvenient that the prior art crushing method needs a taking-out operation under guidance or many coatings with concrete.
Consequently, in a tunnel excavation which requires the destruction of the object to be crushed in accordance with the predetermined line, such a method as explained in FIG. 1 is employed in which a lot of holes (not shown in the drawings) are plugged at a given interval along the shape of the tunnel, into which each hole is injected a jet of water of high pressure to connect with the other holes so as to form slits H to be provided along the predetermined line, and then a blasting powder is inserted into the blast hole S for blasting. However, since this method requires an additional operation for forming the slits in the blast hole, the crushing operation becomes complicated, and moreover, since this method is accompanied with blasting, the generation of noise and/or vibrations cannot be avoided.